Cmp polishing solution and polishing method

ABSTRACT

The present invention relates to a CMP polishing liquid for polishing a substrate comprising at least a barrier metal, a metal film, and a silicon dioxide film or a substrate comprising at least a barrier metal, a metal film, a silicon dioxide film, and a low-k film, wherein: the polishing liquid contains abrasive particles, a metal oxide dissolving agent, an oxidizing agent, a water-soluble polymer, and an alkali metal ion; the surface potentials of the abrasive particles and the metal film upon polishing have the same sign and the product of the surface potential (mV) of the abrasive particles and the surface potential (mV) of the metal film is 250 to 10000; and pH is 7.0 to 11.0.

TECHNICAL FIELD

The present invention relates to a CMP polishing liquid and a polishingmethod using the same.

BACKGROUND ART

Recently, new microfabrication technologies have been developed alongwith higher integration and higher performance of semiconductorintegrated circuits (hereinafter referred to as “LSI”). Chemicalmechanical polishing (hereinafter referred to as “CMP”) method is one ofthe techniques and is a technology frequently used in a LSImanufacturing process, especially, planarization of insulating films,formation of metal plugs, and formation of embedded interconnections ina multilayer interconnection formation process. This technology isdisclosed in Patent Document 1, for example.

Recently, in order to improve the performance of LSI, utilization of ametal film of copper or a copper alloy as a conductive substance to be awiring material has been attempted. However, it is difficult tomicrofabricate copper or a copper alloy by a dry etching methodfrequently used in the formation of conventional aluminum alloy wiring.

Accordingly, a method has been mainly adopted in which a metal film ofcopper or a copper alloy is deposited on and embedded in an insulatingfilm of silicon dioxide or the like in which grooves have been formed inadvance, and the metal film located outside the grooves is removed byCMP to form an embedded interconnection, which is the so-calleddamascene method. This technology is disclosed in Patent Document 2, forexample.

On the other hand, as a barrier metal for preventing diffusion of metalinto the insulating film and improving adhesion, a layer consisting of aconductor such as tantalum, tantalum alloys, or tantalum nitride isformed under the metal film of copper or a copper alloy, etc. Therefore,it is necessary to remove the exposed barrier metal by CMP in a partother than the wiring part in which a metal film of copper or a copperalloy, etc. is embedded.

However, since these barrier metals have higher hardness than copper ora copper alloy, a sufficient polishing rate cannot be obtained even whenpolishing is performed by combining polishing materials for copper or acopper alloy, and the flatness of the surface to be polished is oftendeteriorated. Thus, a two-step polishing method consisting of a firstpolishing step of polishing a metal film and a second polishing step ofpolishing a barrier metal has been investigated.

FIG. 1 is a schematic cross-sectional view showing a wiring formation bya general damascene process. FIG. 1(a) shows a condition beforepolishing, which includes an insulating film 1 having grooves formed onthe surface thereof, a barrier metal 2 formed so as to follow thesurface irregularities of the insulating film 1, and a metal 3 forwiring part of copper or a copper alloy deposited to fill theirregularities.

First, as shown in FIG. 1(b), the metal 3 for wiring part is polishedwith a polishing liquid for polishing the metal for wiring part untilthe barrier metal 2 is exposed (the first polishing step). Next,polishing is performed with a polishing liquid for the barrier metal 2until the convex part of the insulating film 1 is exposed (the secondpolishing step). In this second polishing step, as shown in FIG. 1(c),overpolishing, i.e. excessively polishing the insulating film, is oftenperformed. In FIG. 1(c), symbol 4 indicates the condition of FIG. 1(b)before the barrier metal polishing in the second polishing step. By suchoverpolishing, the flatness of the polished surface after polishing canbe improved.

Proposals for such a polishing liquid for the barrier metal include abarrier metal polishing liquid containing an oxidizing agent, aprotective film forming agent for a metal surface, an acid, and water,the barrier metal polishing liquid having a pH of 3 or less, and theoxidizing agent having a concentration of 0.01 to 3 mass % (for example,see Patent Document 3).

Recently, corrosion of extremely small metal wiring may become a problemalong with miniaturization of wiring intervals. Since corrosion of themetal wiring deteriorates the yield of the LSI, the polishing liquid isalso required to cause no corrosion of the metal wiring. From theviewpoint of yield, few defects on the metal wiring and the insulatingfilm after polishing are also required.

Furthermore, with the recent miniaturization of the wiring intervals, aproblem of wiring delay has arisen. In the integrated circuit, metalwiring is laminated over many layers to transmit signals, and thedistance between the wiring becomes short as miniaturization progresses.As a result, the interwiring capacitance between the adjacent wiresbecomes large and signal delay occurs proportionally to it. This givesrise to a noticeable problem whereby the operation speed of the circuitdoes not increase but the power consumption does.

In order to overcome this problem, as one of the techniques for loweringthe interwiring capacitance, an insulating film having a low dielectricconstant material (hereinafter referred to as “low-k film”) is sometimesused from an insulating film mainly consisting of silicon dioxide.Examples of the low-k film include organosilicate glasses and whollyaromatic ring low-k films. Compared to silicon dioxide films, theselow-k films have disadvantages such as low mechanical strength, highhygroscopicity, low plasma resistance, and low chemical resistance. As aresult, the second polishing step has problems such as damage to thelow-k film, excessive polishing, and film peeling. In order to overcomethe abovementioned problems, it has been proposed to adopt a structurein which a silicon dioxide film is capped on a low-k film. When thesilicon dioxide film of the cap layer is included in the insulating filmpart, the effective relative dielectric constant of the insulating filmas a whole is not lowered so much due to the effect of dielectricconstant of silicon dioxide. For this reason, it is desirable that thesilicon dioxide film as the cap layer is quickly removed at the time ofthe barrier metal polishing and then the insulating film finallyconsists of the only low-k film.

FIG. 2 is a schematic cross-sectional view showing wiring formationusing a low-k film and a cap layer as an insulating film. In order toobtain the structure of FIG. 2(a), a low-k film 6 and a cap layer 7consisting of silicon dioxide are formed in a laminated structure on aSi substrate 5, and then the raised part and the groove part are formed.The barrier metal 2 is formed thereon so as to follow the raised partand the groove part of the surface, and the wiring part metal 3deposited entirely so as to fill the raised part and the groove part isformed.

As in FIG. 1, from the condition of the substrate shown in FIG. 2(a) tothe condition of the substrate shown in FIG. 2(b), the wiring part metal3 is polished by the polishing liquid for polishing the wiring partmetal until the barrier metal 2 is exposed (the first polishing step).As shown in FIG. 2(c), the barrier metal 2 is polished with thepolishing liquid for the bather metal to reach the condition of thesubstrate shown in FIG. 2(c), that is, at least the cap layer 7consisting of silicon dioxide is completely removed and until the low-kfilm 6 is exposed (the second polishing step).

Accordingly, in the second polishing step, it is necessary to polish thebarrier metal, the metal film, and the silicon dioxide film, or thebarrier metal, the metal film, the silicon dioxide film which is the caplayer, and the low-k film. The polishing rate for the low-k film tendsto be large for reasons such as low mechanical strength and chemicalresistance. Since the low-k film should not be excessively removedunlike the cap layer, the polishing rate for the low-k film is requirednot to be too large. When the polishing rate for the metal film is toolarge, the central part of the embedded metal wiring is isotopicallypolished to cause the phenomenon (dishing) in which the central partbecomes depressed like a dish. It is thus required also for thepolishing rate for the metal film not to be too large.

CITATION LIST Patent Literature

Patent Document 1: U.S. Pat. No. 4,944,836Patent Document 2: Japanese Unexamined Patent Publication No. H2-278822Patent Document 3: International Publication No. WO 01/13417 pamphlet

SUMMARY OF INVENTION Technical Problem

As described above, the barrier metal, the metal film, and the silicondioxide film, or the barrier metal, the metal film, the silicon dioxidefilm as the cap layer, and the low-k film may be polished by using thepolishing liquid for the barrier metal. Therefore, a certain uniformpolishing rate is required for the polishing liquid for the barriermetal, the metal film, the silicon dioxide film, and the low-k film, andparticularly the polishing rates for the metal film and the low-k filmare required to be appropriately controlled (not too high). However,since the mechanical strength of the barrier metal or the silicondioxide is generally relatively high, the polishing rates for thebarrier metal and the silicon dioxide film are low and the polishingrates for the metal film and the low-k film tend to be high. For thisreason, it is difficult to adapt the CMP polishing liquid for individualfilms as the polishing target, and to balance the polishing rate foreach film.

The present invention has been made in view of the abovementionedproblems, and the object of the present invention is to provide a CMPpolishing liquid capable of suppressing corrosion of the metal film andoccurrence of defects on the metal film and the insulating film anduniformly polishing the barrier metal, the metal film, the silicondioxide film, and the low-k film at a high polishing rate in the secondpolishing step polishing the barrier metal, and a polishing method usingthe polishing liquid.

Solution to Problem

The polishing liquid according to the present invention is a CMPpolishing liquid for polishing a substrate comprising at least a barriermetal, a metal film, and a silicon dioxide film, or a substratecomprising at least a barrier metal, a metal film, a silicon dioxidefilm, and a low-k film, wherein the polishing liquid contains abrasiveparticles, a metal oxide dissolving agent, an oxidizing agent, awater-soluble polymer, and an alkali metal ion; the surface potentialsof the abrasive particles and the metal film have the same sign and theproduct of the surface potential (mV) of the abrasive particles and thesurface potential (mV) of the metal film is 250 to 10000; and pH is 7.0to 11.0.

In one embodiment of the present invention, it is preferable that theabrasive particles form associated particles, and the average secondaryparticle diameter of the associated particles is 120 nm or less.

In one embodiment of the present invention, it is preferable that thecontent of abrasive particles is 1 to 20 mass %.

In one embodiment of the present invention, it is preferable thatabrasive particles comprise silica particles.

In one embodiment of the present invention, it is preferable that themetal oxide dissolving agent comprise at least one selected from thegroup consisting of citric acid, malonic acid, diglycolic acid,isophthalic acid, and methylsuccinic acid.

In one embodiment of the present invention, it is preferable that thewater-soluble polymer have a structure of the following formula (1):

RO—X_(n)—Y_(m)—H  (1)

(In the formula, R represents an alkyl group, an alkenyl group, a phenylgroup, a polycyclic phenyl group, an alkylphenyl group, or analkenylphenyl group having 6 or more carbon atoms, X and Y represent anoxyethylene group and an oxypropylene group that optionally have asubstituent on a side chain, respectively, n and m each represent aninteger of 0 or more, and n+m is an integer of 4 or more).

In one embodiment of the present invention, it is preferable that thealkali metal ion be a potassium ion.

In addition, a polishing method of the present invention ischaracterized by comprising a step of relatively moving a polishingplaten and a substrate in a condition where the substrate is pressedagainst the polishing cloth, while the abovementioned CMP polishingliquid is supplied onto the polishing cloth of the polishing platen, thesubstrate comprising at least a barrier metal, a metal film, and asilicon dioxide film, or comprising at least a barrier metal, a metalfilm, a silicon dioxide film, and a low-k film.

Advantageous Effects of Invention

The present invention can provide the CMP polishing liquid capable ofsuppressing corrosion of the metal film and occurrence of defects on themetal film and the insulating film, and uniformly polishing the barriermetal, the metal film, the silicon dioxide film and the low-k film at ahigh polishing rate in the second polishing step of polishing thebarrier metal, and the polishing method using the polishing liquid.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing wiring formation by ageneral damascene process.

FIG. 2 is a schematic cross-sectional view showing wiring formationusing the low-k film and the cap layer as the insulating film.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed. However, the present invention is not limited to thefollowing embodiments at all.

(CMP Polishing Liquid)

The CMP polishing liquid according to the present embodiment containsabrasive particles, a metal oxide dissolving agent and, as a chemicalcomponent, a metal corrosion inhibitor, an oxidizing agent, awater-soluble polymer and an alkali metal ion.

(Abrasive Particle)

The primary particle diameter of abrasive particles is preferable to be80 nm or less, more preferable to be 5 to 70 nm, particularly preferableto be 10 to 65 nm, and extremely preferable to be 15 to 60 nm. Theabrasive particles may form associated particles, and the averagesecondary particle diameter of the associated particles is preferable tobe 120 nm or less, more preferable to be 5 to 100 nm, particularlypreferable to be 10 to 90 nm, and extremely preferable to be 15 to 80nm. When the secondary particle diameter exceeds 120 nm, the polishingrate tends to deteriorate. The secondary particle diameter of theabrasive particles is measured using a light diffraction scattering typeparticle size distribution meter (for example, N5 manufactured byBECKMAN COULTER).

The content of abrasive particles (content based on the total mass ofthe CMP polishing liquid, the same applies hereinafter) is preferable tobe 1 to 20 mass %, more preferable to be 1.5 to 18 mass %, andparticularly preferable to be 2.0 to 15 mass %. When the content is lessthan 1 mass %, the ability to remove the mechanical reaction layer byabrasive particles is insufficient and the polishing rate for thesilicon dioxide film and the barrier metal tends to be low.

It is preferable that the abrasive particles comprise silica particles.Conventionally, silica, alumina, ceria, and the like are well known asmaterials of abrasive particles, but silica is preferable because it isdifficult to cause defects on the surface of the metal film and theinsulating film after polishing. As the material of abrasive particles,it is also possible to use silicas (for example, particles coated with apolymer on silica surface).

(Metal Oxide Dissolving Agent)

The metal oxide dissolving agent is preferable to be water soluble, andexamples thereof include organic acids such as malonic acid, citricacid, malic acid, glycolic acid (diglycolic acid), glutamic acid,glyconic acid, oxalic acid, tartaric acid, picolinic acid, nicotinicacid, mandelic acid, picolinic acid, acetic acid, formic acid, succinicacid, adipic acid, glutaric acid, benzoic acid, quinaldic acid, butyricacid, valeric acid, lactic acid, phthalic acid, fumaric acid, maleicacid, aminoacetic acid, salicylic acid, glyceric acid, and pimelic acid;these organic acid esters; salts of these organic acids; inorganic acidssuch as sulfuric acid, nitric acid, phosphoric acid, acetic acid, andhydrochloric acid; and salts of these inorganic acids. These can be usedsingly or in admixture of two or more. Of these, citric acid, malonicacid, diglycolic acid, isophthalic acid, and methylsuccinic acid arepreferable from the viewpoint of improving the polishing rate for thebarrier metal and the silicon dioxide film. These can be used singly orin combination of two or more.

The content of the metal oxide dissolving agent is preferable to be0.005 to 5 mass %, more preferable to be 0.01 to 3 mass %, andparticularly preferable to be 0.1 to 2 mass %. When this content is lessthan 0.005 mass %, the effect on improving the polishing rate for thesilicon dioxide film is low, and when it exceeds 5 mass %, abrasiveparticles tend to aggregate and the storage stability tends to decrease.

(Water-Soluble Polymer)

It is preferable that the water-soluble polymer have a structure of thefollowing formula (1):

RO—X_(n)—Y_(m)—H  (1)

In the formula, R represents an alkyl group, an alkenyl group, a phenylgroup, a polycyclic phenyl group, an alkylphenyl group, or analkenylphenyl group having 6 or more carbon atoms.

In the formula, X represents an oxyethylene group and Y represents anoxypropylene group. A substituent such as an alkyl group or a phenylgroup may be bonded to the side chain in the oxyethylene group or theoxypropylene group. In addition, n and m represent the number ofrepeating structures of the oxyethylene group and the oxypropylenegroup, each of n and m is an integer of 0 or more, and n+m is an integerof 4 or more.

The weight average molecular weight of the water-soluble polymer ispreferable to be 100 to 30000, more preferable to be 200 to 20000, andparticularly preferable to be 300 to 10000. When the molecular weight isless than 100 or exceeds 30000, the effect of adjusting the polishingrate for the low-k film tends to be small. The content thereof ispreferable to be 0.001 to 0.5 mass %, more preferable to be 0.002 to 0.3mass %, and particularly preferable to be 0.004 to 0.2 mass %. When thecontent is less than 0.001 mass %, the effect of adjusting the polishingrate for the low-k film is small, and when it exceeds 0.5 mass %,abrasive particles tend to aggregate and the storage stability tends todecrease.

(Oxidizing Agent)

In the present embodiment, it is preferable to use an oxidizing agentfor adjusting the polishing rate for the metal film. Examples of theoxidizing agent for the metal film in the present embodiment includehydrogen peroxide (H₂O₂), potassium periodate, ammonium persulfate,hypochlorous acid, and ozone water. These can be used singly or incombination of two or more, but an oxidizing agent containing nononvolatile components is desirable, since contamination with halides orthe like is undesirable. Among them, hydrogen peroxide is preferablefrom the viewpoint of stability.

(pH of CMP Polishing Liquid)

The pH of the CMP polishing liquid is preferable to be 7.0 to 11.0, morepreferable to be 7.5 to 10.7, and particularly preferable to be 8.0 to10.5. When the pH is less than 7 or exceeds 11.0, corrosion to the metalfilm tends to occur.

(Alkali Metal Ion)

As the alkali metal ion of the present embodiment, a lithium ion, asodium ion, a potassium ion, and a rubidium ion are preferable to beused, and a potassium ion is particularly preferable from the viewpointof not contaminating the semiconductor device.

An alkali metal ion is used as a pH adjusting agent for the CMPpolishing liquid. As a pH adjusting agent containing an alkali metalion, potassium hydroxide or the like can be suitably used. Ammonia,organic amines, and the like exist as a pH adjusting agent, but whenthese are used, the polishing rate for the metal film is remarkablydeteriorated and odor is likely to occur. There is also a pH adjustingagent containing an alkaline earth metal and the like, but these tend tocause aggregation of abrasive particles.

The alkali metal ion content is preferable to be 0.01 mass % or more,and particularly preferable to be 0.03 mass % or more. From theviewpoint of preventing aggregation of silica, it is preferable to beless than 2 mass % and particularly preferable to be less than 1.9 mass%.

(Surface Potential)

The surface potential (mV) of the metal film formed by a chemicalcomponent contained in the CMP polishing liquid and the surfacepotential (mV) of abrasive particles, obtained by the surface potentialmeasuring device, have the same sign, and the product is preferable tobe 250 to 10000, preferable to be 300 to 10000, and particularlypreferable to be 400 to 10000. Since the both surface potentials havethe same sign and the product is within the above range; abrasiveparticles electrostatically repel the metal film and the insulatingfilm; adhesion derived from abrasive particles can be suppressed afterpolishing; and adhesion of abrasive particles can be suppressed, defectson the metal film surface and the insulating film can be suppressed.

(Metal Corrosion Inhibitor)

The CMP polishing liquid according to the present embodiment may containa metal corrosion inhibitor or the like as other additives. As a metalcorrosion inhibitor, the compound capable of forming a chelate complexwith a metal and forming a protective film that prevents excessiveetching of the metal can be used. As such a compound, a known compoundcan be used, and examples thereof include a compound having a triazoleskeleton, a compound having an imidazole skeleton, a compound having apyrimidine skeleton, a compound having a guanidine skeleton, a compoundhaving a thiazole skeleton, and a compound having a pyrazole skeleton.These metal corrosion inhibitors can be used singly or in admixture oftwo or more.

Examples of the compound having a triazole skeleton include1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole,benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole,2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole,4-carboxyl(-1H-)benzotriazole, 4-carboxyl(-1H-)benzotriazole methylester, 4-carboxyl(-1H-)benzotriazole butyl ester,4-carboxyl(-1H-)benzotriazole octyl ester, 5-hexylbenzotriazole,[1,2,3-benzotriazolyl-1-methyl][1,2,4-triazolyl-1-methyl][2-ethylhexyl]amine,tolyltriazole, naphthotriazole, bis[(1-benzotriazolyl)methyl]phosphonicacid, 3-aminotriazole, and 5-methylbenzotriazole.

Examples of the compound having an imidazole skeleton include2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole,2-propylimidazole, 2-butylimidazole, 4-methylimidazole,2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole,and 2-aminoimidazole.

Examples of the compound having a pyrimidine skeleton includepyrimidine, 1,2,4-triazolo[1,5-a]pyrimidine,1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine,1,3-diphenyl-pyrimidine-2,4,6-trione, 1,4,5,6-tetrahydropyrimidine,2,4,5,6-tetraaminopyrimidine sulfate, 2,4,5-trihydroxy pyrimidine,2,4,6-triaminopyrimidine, 2,4,6-trichloropyrimidine,2,4,6-trimethoxypyrimidine, 2,4,6-triphenylpyrimidine,2,4-diamino-6-hydroxyl pyrimidine, 2,4-diaminopyrimidine,2-acetamidopyrimidine, 2-aminopyrimidine,2-methyl-5,7-diphenyl-(1,2,4)triazolo[1,5-a]pyrimidine,2-methylsulfanyl-5,7-diphenyl-(1,2,4)triazolo[1,5-a]pyrimidine,2-methylsulfanyl-5,7-diphenyl-4,7-dihydro-(1,2,4)triazolo[1,5-a]pyrimidine,and 4-aminopyrazolo[3,4-d]pyrimidine.

Examples of the compound having a guanidine skeleton include1,3-diphenylguanidine and 1-methyl-3-nitroguanidine.

Examples of the compound having a thiazole skeleton include2-mercaptobenzothiazole, 2-aminothiazole, 4,5-dimethylthiazole,2-amino-2-thiazoline, 2,4-dimethylthiazole, and2-amino-4-methylthiazole.

Examples of the compound having a pyrazole skeleton include3,5-dimethylpyrazole, 3-methyl-5-pyrazolone, 3-amino-5-methylpyrazole,3-amino-5-hydroxypyrazole, and 3-amino-5-methylpyrazole.

Among them, the compound having a triazole skeleton is preferable fromthe viewpoint of the polishing rate and the etching rate. Among thecompounds having a triazole skeleton, 1,2,3-triazole, 1,2,4-triazole,3-amino-1H-1,2,4-triazole, 4-amino-4H-1,2,4-triazole, benzotriazole,1-hydroxybenzotriazole, and 5-methylbenzotriazole are more preferable.

The content of the metal corrosion inhibitor is preferable to be 0.001mass % or more, more preferable to be 0.002 mass % or more, and stillmore preferable to be 0.004 mass % or more from the viewpoint of easysuppression of etching, and preferable to be 1.0 mass % or less, morepreferable to be 0.5 mass % or less, and still more preferable to be 0.3mass % or less from the viewpoint of obtaining a practical level ofpolishing rate.

(The Film to be Polished)

Examples of the material of the metal film include those containingmetals such as copper, copper alloy, copper oxide or copper alloy oxide,cobalt, cobalt alloy, tungsten, tungsten alloy, silver, and gold as amain component. As the metal film, a film formed by a known sputteringmethod, a plating method, or the like can be used.

The barrier metal is formed in order to prevent the metal of the wiringmetal from diffusing into the insulating film and to improve theadhesion between the insulating film and the wiring metal. Thecomposition of the barrier metal is preferable to be selected fromtungsten compounds such as tungsten, tungsten nitride, and tungstenalloys; titanium compounds such as titanium, titanium nitride, andtitanium alloys; tantalum compounds such as tantalum, tantalum nitride,and tantalum alloys; ruthenium; ruthenium compounds; cobalt; and cobaltcompounds. The barrier metal may have a single layer structureconsisting of one of these or a laminated structure consisting of two ormore.

As the insulating film, there are the silicon dioxide film and the low-kfilm Examples of the low-k film include a silicon-based film and anorganic polymer film. Examples of the silicon-based film as the low-kfilm include a silica-based film such as a silicon oxide film,fluorosilicate glass, organosilicate glass obtained usingtrimethylsilane or dimethoxydimethylsilane as a starting material, andporous organosilicate glass. Examples of the organic polymer film as thelow-k film include a wholly aromatic low dielectric constant interlayerinsulating film. From the viewpoint of solving the wiring delay, it ispreferable that the dielectric constant is 2.9 or less. Among them,fluorosilicate glasses, organosilicate glasses, porous organosilicateglasses, and the like are particularly used as the low-k film. Thesefilms are formed by a CVD method, a spin coating method, a dip coatingmethod, or a spraying method.

The polishing method of the present embodiment is a polishing method inwhich, while the above CMP polishing liquid is supplied onto a polishingcloth of a polishing platen, the film to be polished is polished byrelatively moving the polishing platen and the substrate in a conditionwhere the substrate having the film to be polished is pressed againstthe polishing cloth. More specifically, the polishing method of thepresent embodiment is a polishing method that comprises a step of, whilethe above CMP polishing liquid is supplied onto the polishing cloth ofthe polishing platen, relatively moving the polishing platen and thesubstrate in a condition where the substrate is pressed against thepolishing cloth, the substrate comprising at least a barrier metal, ametal film, and a silicon dioxide film or comprising at least a barriermetal, a metal film, a silicon dioxide film, and a low-k film. As anapparatus for polishing, for example, a general polishing apparatushaving the platen to which the polishing cloth (pad) and a motor or thelike capable of changing the rotation speed are attached and having aholder for holding the substrate can be used. The polishing cloth is notparticularly limited, but general nonwoven fabric, foamed polyurethane,porous fluororesin, or the like can be used. The polishing conditionsare not particularly limited, but it is preferable to set the rotationspeed of the platen to a low rotation of 200 rpm or less so that thesubstrate does not jump out.

The polishing pressure on the polishing cloth of the substrate havingthe film to be polished is preferable to be 3 to 100 kPa, and morepreferable to be 5 to 50 kPa from the viewpoint of uniformity of thepolishing rate in the substrate surface and flatness of the pattern. Itis preferable to continuously supply the CMP polishing liquid to thepolishing cloth with a pump or the like during polishing. This supplyamount is not limited, but it is preferable that the surface of thepolishing cloth is always covered with the polishing liquid. In order tocarry out chemical mechanical polishing with the surface condition ofthe polishing cloth always kept constant, it is preferable to put theconditioning step of the polishing cloth before polishing or duringpolishing. For example, conditioning of the polishing cloth is performedwith a liquid containing at least water by using a dresser havingdiamond particles. Subsequently, it is preferable to carry out thepolishing method of the present embodiment and further add a substratecleaning step.

EXAMPLES

Hereinafter, the present invention will be described in detail byexamples, but the present invention is not limited to these examples.

Examples 1 to 4 and Comparative Examples 1 to 5

The silica described in Table 1 was used as abrasive particles. Theaverage secondary particle diameter (average secondary particle diameterof associated particles) of the silica (silica A and silica B) describedin Table 1 was measured using N5 manufactured by BECKMAN COMER. For themeasuring method, a photon correlation method was used, and the materialcontaining silica was diluted so that the scattering intensity was5.0×10⁴ to 1.0×10⁶ cps, and the material was placed in a plastic celland the particle diameter was measured.

TABLE 1 Average secondary particle diameter (nm) Silica A 66 Silica B 61

Example 1

Malonic acid of 0.4 mass %, 0.0065 mass % of BTA (benzotriazole), and0.0065 mass % of polyoxyethylene tridecyl ether (n=8 and m=0 in theabove formula (1), the same applies to the following) were added todeionized water, and this was added with 1.5 mass % of KOH, then 7.5mass % of silica A, and finally 0.1 mass % of hydrogen peroxide toprepare the CMP polishing liquid 1. The pH of the CMP polishing liquidwas 10.

Example 2

Diglycolic acid of 0.4 mass %, 0.0065 mass % of HBTA(1-hydroxybenzotriazole), and 0.0065 mass % of polyoxyethylene tridecylether were added to deionized water, and this was added with 1.26 mass %of KOH, then 7.5 mass % of silica A, and finally 0.1 mass % of hydrogenperoxide to prepare the CMP polishing liquid 2. The pH of the CMPpolishing liquid was 10.

Example 3

Diglycolic acid of 0.22 mass %, 0.0040 mass % of HBTA, and 0.0065 mass %of polyoxyethylene tridecyl ether were added to deionized water, andthis was added with 0.73 mass % of KOH, then 5.0 mass % of silica B, andfinally 0.1 mass % of hydrogen peroxide to prepare the CMP polishingliquid 3. The pH of the CMP polishing liquid was 10.

Example 4

Malonic acid of 0.40 mass % and 0.0065 mass % of polyoxyethylenetridecyl ether were added to deionized water, and this was added with1.50 mass % of KOH, then 7.5 mass % of silica A, and finally 0.1 mass %of hydrogen peroxide to prepare the CMP polishing liquid 4. The pH ofthe CMP polishing liquid was 10.

Comparative Example 1

The CMP polishing liquid 5 was prepared in the same manner as in Example1 except that malonic acid was not added as a metal oxide dissolvingagent and the addition amount of KOH as a pH adjusting agent was changedto 0.35 mass %. The pH of the CMP polishing liquid 5 was 10.

Comparative Example 2

The CMP polishing liquid 6 was prepared in the same manner as in Example1 except that polyoxyethylene tridecyl ether was not added as an organiccompound. The pH of the CMP polishing liquid 6 was 10.

Comparative Example 3

The CMP polishing liquid 7 was prepared in the same manner as in Example1 except that KOH as the alkali metal ion source and a pH adjustingagent was changed to monoethanolamine. The pH of the CMP polishingliquid 7 was 10.

Comparative Example 4

The CMP polishing liquid 8 was prepared in the same manner as in Example1 except that hydrogen peroxide was not added as an oxidizing agent. ThepH of the CMP polishing liquid 8 was 10.

Comparative Example 5

Malonic acid of 0.4 mass %, 0.0065 mass % of BTA, and 0.0065 mass % ofpolyoxyethylene tridecyl ether were added to deionized water, and thiswas added with 0.05 mass % of KOH, then 3.0 mass % of silica A, andfinally 0.1 mass % of hydrogen peroxide to prepare the CMP polishingliquid 9. The pH of the CMP polishing liquid 9 was 3.0.

(Polishing Condition)

Polishing pad: H 7000 (Fujibo Co., Ltd.)

Polishing pressure: 10.3 kPa

Platen rotation speed: 90 rpm

Head rotation speed: 87 rpm

Polishing liquid supply amount: 300 ml

(Polishing Rate Evaluation Substrate)

Metal film: A 12-inch Cu substrate having copper (Cu) film of 1500 nm inthickness formed on a silicon substrateBarrier metal: A 12-inch TaN substrate having tantalum nitride (TaN)film of 200 nm in thickness formed on a silicon substrateLow-k film: A 12 inch low-k substrate having low-k film of 500 nm inthickness formed on a silicon substrate (trade name “Black Diamond”,manufactured by Applied Materials, Inc.)Silicon dioxide film (cap film): A 12-inch TEOS substrate having a TEOSfilm of 1000 nm in thickness formed on a silicon substrate

(Polishing Rate and Selectivity Ratio)

The Cu polishing rate and the polishing rate for TaN were determined bycalculating the difference in film thickness between before and afterCMP of Cu and TaN from the electric resistance value obtained using theresistance measuring device, VR-120/08S (manufactured by Hitachi KokusaiElectric Inc.). TEOS and low-k were determined from the film thicknessdifference before and after polishing using the optical interferencefilm thickness measuring device, F80 (manufactured by Filmetrics). Inthe CMP under the same conditions, the polishing rate forCu/TaN/low-k/TEOS is preferable to be (20 to 120 nm/min)/(40 to 120nm/min)/(40 to 120 nm/min)/(40 to 120 nm/min).

As the selectivity ratio of the polishing rate, the polishing rate ratiofor Cu/TaN/low-k film/TEOS is preferable to be (0.3 to 1.5)/1.0/(0.5 to2.0)/(0.3 to 1.5).

(Evaluation of Corrosion Rate of Cu)

The corrosion rate of Cu was calculated from difference in filmthickness before and after immersion and immersion time obtained byattaching a Cu substrate cut to 20 mm square to a stirring spring andimmersing the Cu substrate in a polishing liquid warmed at 60° C. for 5minutes at 100 rpm of the rotational speed of the stirring spring.

(Method for Measuring Surface Potential)

The surface potential of silica was measured using the surface potentialmeasuring device, Delsa Nano C manufactured by BECKMAN COULTER. For themeasurement method, laser Doppler multipoint detection typeelectrophoresis method was used, and the measurement range was ±100 mV.The polishing liquid was diluted so that the scattering intensity became1.0×10⁴ to 5.0×10⁴ cps, and placed in a quartz cell for measuring thesurface potential of the dilute solution, and measurement was carriedout at 25° C.

Since Cu is assumed to be copper oxide by the oxidizing agent uponpolishing, the surface potential was measured by adding 1 mass % ofcopper oxide (II) powder (manufactured by KANTO CHEMICAL CO., INC.) inthe CMP polishing liquid without abrasive particles, being kept for 5minutes, collecting the supernatant with a pipette, and injecting 3 mLof the supernatant into a measurement cell.

(Evaluation of Defects on Cu (Metal Film) and TEOS (Insulating Film)Surface)

The number of surface defects of Cu and TEOS was measured under thefollowing conditions using LS 6700 manufactured by Hitachi ElectronicsEngineering Co., Ltd. The number of surface defects after polishing/thenumber of surface defects before polishing was calculated, and thenumber of 2.0 or more was judged to be defective.

Defect measurement range of Cu surface: 0.200 μm-0.370 μmDefect measurement range of TEOS surface: 0.200 μm-0.808 μm

In Examples 1 to 4 and Comparative Examples 1 to 5, the evaluationresults for the polishing rate and the selectivity ratio of thepolishing rate for Cu, TaN, low-k, and TEOS; surface potential of Cu andsilica and its product; the corrosion rate of Cu; and the ratio of thenumber of Cu and TEOS surface defects before and after polishing areshown in Tables 2 and 3.

TABLE 2 Item Example 1 Example 2 Example 3 Example 4 CompositionAbrasive grain Silica A Silica A Silica B Silica A Content (mass %) 7.57.5 5.0 7.5 Metal oxide dissolving Malonic acid Diglycolic acidDiglycolic acid Malonic acid agent Content (mass %) 0.40 0.40 0.22 0.40Metal corrosion BTA HBTA HBTA — inhibitor Content (mass %) 0.0065 0.00650.0040 — Water-soluble polymer Polyoxyethylene PolyoxyethylenePolyoxyethylene Polyoxyethylene tridecyl ether tridecyl ether tridecylether tridecyl ether Content (mass %) 0.0065 0.0065 0.0065 0.0065 pHadjusting agent KOH KOH KOH KOH Content (mass %) 1.50 1.26 0.73 1.50Alkali metal ion Potassium Potassium Potassium Potassium Content (mass%) 0.51 0.43 0.16 0.51 Oxidizing agent 0.1 0.1 0.1 0.1 (hydrogenperoxide) (mass %) pH 10.0 10.0 10.0 10.0 Polishing rate Cu (nm/min) 8769 49 98 TaN (nm/min) 77 71 56 79 low-k (nm/min) 99 104 53 99 TEOS(nm/min) 84 78 49 84 Selectivity Cu/TaN/low-k/TEOS 1.1/1.0/1.3/1.11.0/1.0/1.5/1.1 0.9/1.0/0.9/0.9 1.2/1.0/1.3/1.1 ratio Surface Cu (mV)−17 −20 −22 −18 potential Silica (mV) −52 −49 −35 −47 Product of surface884 980 770 846 potential Corrosion rate of Cu (60° C.) ≤1.0 ≤1.0 ≤1.0≤1.0 Ratio of Cu 1.43 1.32 0.82 0.75 surface defect TEOS 0.66 0.52 0.820.70 number before and after polishing

TABLE 3 Comparative Comparative Comparative Comparative Comparative ItemExample 1 Example 2 Example 3 Example 4 Example 5 Composition Abrasivegrain Silica A Silica A Silica A Silica A Silica A Content (mass %) 7.57.5 7.5 7.5 3.0 Metal oxide — Malonic acid Malonic acid Malonic acidMalonic acid dissolving agent Content (mass %) — 0.40 0.40 0.40 0.40Metal corrosion BTA BTA BTA BTA BTA inhibitor Content (mass %) 0.00650.0065 0.0065 0.0065 0.0065 Water-soluble Polyoxyethylene —Polyoxyethylene Polyoxyethylene Polyoxyethylene polymer tridecyl ethertridecyl ether tridecyl ether tridecyl ether Content (mass %) 0.0065 —0.0065 0.0065 0.0065 pH adjusting agent KOH KOH Monoethanolamine KOH KOHContent (mass %)) 0.35 1.50 1.95 1.50 0.05 Alkali metal ion PotassiumPotassium — Potassium Potassium Content (mass %) 0.12 0.51 — 0.51 0.10Oxidizing agent 0.1 0.1 0.1 — 0.1 (hydrogen peroxide) (mass %) pH 10.010.0 10.0 10.0 3.0 Polishing Cu (nm/min) 41 67 242 10 83 rate TaN(nm/min) 20 56 58 58 72 low-k (nm/min) 15 159 95 95 49 TEOS (nm/min) 1570 63 63 68 Selectivity Cu/TaN/low-k/TEOS 2.1/1.0/0.8/0.81.2/1.0/2.8/1.2 4.2/1.0/1.6/1.1 0.2/1.0./1.6/1.1 1.2/1.0/0.7/0.9 ratioSurface Cu (mV) — — — — −30 potential Silica (mV) — — — — 2 Product ofsurface — — — — −60 potential Corrosion rate of Cu (60° C.) ≤1.0 ≤1.0≤1.0 ≤1.0 ≤15 Ratio of Cu — — — — 0.98 surface TEOS — — — — 2.09 defectnumber before and after polishing

(Evaluation Result)

In Examples 1 to 4, the polishing rates for TaN and TEOS were high, thepolishing rates for Cu and low-k were also comparable to those for TaNand TEOS, and both the polishing rate and the selectivity ratio ofpolishing rate were good. There was no corrosion of Cu, and the defectsof Cu and TEOS surfaces also had low values. On the other hand, inComparative Example 1 in which the metal oxide dissolving agent was notadded, the polishing rates for TEOS and TaN were extremely low values.In Comparative Example 2 in which no water-soluble polymer was added,the polishing rate for low-k was 159 nm/min, which was a very largevalue. In Comparative Example 3, monoethanolamine was used instead ofpotassium hydroxide, which is a pH adjusting agent as a potassium ionsource, but the polishing rate for Cu significantly increased. InComparative Example 4, no oxidizing agent was added, but the polishingrate for Cu was significantly low. In Comparative Example 5, althoughthe product of the surface potential had a negative value, the corrosionrate to Cu was high and the number of defects on the TEOS surface alsobecame high.

From the above results, the CMP polishing liquid and the polishingmethod of the present invention can not only polish TaN (barrier metal)and TEOS (insulating film or cap layer) at high speed, but also controlthe polishing rate for Cu (metal film) and low-k (low dielectricconstant film) appropriately (so that the polishing rate does not becometoo high). The CMP polishing liquid of the present invention does notcorrode Cu (metal film) and can suppress defects on the surfaces of Cu(metal film) and TEOS (insulating film).

REFERENCE SIGNS LIST

-   1: Insulating film-   2: Barrier metal-   3: Wiring part metal-   5: Si substrate-   6: Low-k film-   7: Cap layer

1. A CMP polishing liquid for polishing a substrate comprising at leasta barrier metal, a metal film, and a silicon dioxide film or a substratecomprising at least a barrier metal, a metal film, a silicon dioxidefilm, and a low-k film, wherein: the polishing liquid contains abrasiveparticles, a metal oxide dissolving agent, an oxidizing agent, awater-soluble polymer, and an alkali metal ion; surface potentials ofthe abrasive particles and the metal film upon polishing have the samesign and a product of the surface potential (mV) of the abrasiveparticles and the surface potential (mV) of the metal film is 250 to10000; and pH is 7.0 to 11.0.
 2. The polishing liquid according to claim1, wherein the abrasive particles form associated particles and anaverage secondary particle diameter of the associated particles is 120nm or less.
 3. The polishing liquid according to claim 1, wherein acontent of the abrasive particles is 1 to 20 mass %.
 4. The polishingliquid according to claim 1, wherein the abrasive particles comprisesilica particles.
 5. The polishing liquid according to claim 1, whereinthe metal oxide dissolving agent comprises at least one selected fromthe group consisting of citric acid, malonic acid, diglycolic acid,isophthalic acid, and methylsuccinic acid.
 6. The polishing liquidaccording to claim 1, the water-soluble polymer has a structure of thefollowing formula (1):RO—X_(n)—Y_(m)—H  (1) wherein R represents an alkyl group, an alkenylgroup, a phenyl group, a polycyclic phenyl group, an alkylphenyl group,or an alkenylphenyl group having 6 or more carbon atoms; X and Yrepresent an oxyethylene group and an oxypropylene group that optionallyhave a substituent on a side chain, respectively; n and m each representan integer of 0 or more; and n+m is an integer of 4 or more.
 7. Thepolishing liquid according to claim 1, wherein the alkali metal ion is apotassium ion.
 8. A polishing method comprising a step of relativelymoving a polishing platen and a substrate in a condition where thesubstrate is pressed against the polishing cloth, while the CMPpolishing liquid according to claim 1 is supplied onto the polishingcloth of the polishing platen, the substrate comprising at least abarrier metal, a metal film, and a silicon dioxide film or comprising atleast a barrier metal, a metal film, a silicon dioxide film, and a low-kfilm.